The Clinical Laboratory Core will be the central clinical laboratory for the clinical studies of this Program Project. The Core will provide the following essential sample processing and diagnostic services for Projects 1, 2, and 3: * Processing of blood and tissue samples, including separation of plasma and peripheral blood mononuclear cells (PBMC), separation of PBMC subpopulations by magnetic bead sorting, coordination of clinical hematology and biochemistry studies, and coordination of specimen storage and shipment to the other project sites. * Performance of serologic and virologic assays for detection of dengue virus and anti-dengue antibodies, including enzyme immunoassays, hemagglutination inhibition assays, neutralizing antibody assays, qualitative RT-PCR, and virus isolation in Toxorrhynchities splendens mosquitoes. * Performance of fluorogenic RT-PCR for quantification of dengue virus RNA in plasma, sera, and mosquitoes. * Performance of flow cytometry analyses on fresh blood samples for PBMC subsets, activation marker expression, and detection of dengue antigen-specific T lymphocytes.